Photomechanical bleachout color process



June 6, 1967 D. sTRAw ETAL 3,323,917

PHOTOMECHANICAL BLEACHOUT COLOR PROCESS Filed March '7, 1963 FIG.4

FIGB

FIG.5

FIG.6

FIG.7

INVENT ORS GLAS STRAW FORD E. HERRICK,JR.

ATTORNEYS United States Patent O Delaware Filed Mar. 7, 1963, Ser. No. 263,563 4 Claims. (Cl. 96-27) The present invention relates to a photomechanical bleachont color process. It has particular application to a positive working photomechanical bleachout process which is capable of yielding high-contrast images in a number of colors. Y

A widely used, modern technique in color reproduction is the diazotype system, which involves the use of a so-called intermediate. In place of making a large number of copies from a frail and valuable original, it is customary to make a single copy on an intermediate material or support. From this, additional prints, can be made.

A thin material, such .as a foil, -is frequently used and in order to be satisfactory as an intermediate material, this should have the fastest possible printing speed consistent with good opacity. It should be stabilized against precoupling, or yellowing, or offsetting tendencies. A vary satisfactory product of this type has been disclosed in application Ser. No. 641,023 led Feb. 19, 1957 now Patent No. 2,940,852. Materials of the type disclosed in this application satisfy many of the requirements, but they frequently suffer from slow printing speeds and yield prints of only mediocre to fair contrast.

These properties of slow printing speeds and inadequate contrast are particularly disadvantageous in graphic art applications. In these, printing exposures are necessarily made under a vacuum contact with an arc lamp in order to insure good resolution. These devices require considerable exposure time, `as much as several minutes. The amount of light-sensitive material present in the lightsensitive layer or the amount of material photodecomposed therein is directly related to the image density. Also, although the contrast of diazotype materials is normally considered quite good in comparison to conventional silver halide photographs, it is only marginally acceptable in certain graphic art applications where there is a higher requirement for contrast.

Diazotype foils, or intermediates which are capable of bearing images in different colors, are used for `the pretesting and proofing of half-tone color separation positives. Such materials are used in the production of color printing plates for offset, letterpress or gravure printing. It is well known that such positive half-tone color separation films, or plates, normally require a certain amount of hand correction. In other words, they must be touched up to reproduce faithfully the colors of the original subject or scene in terms of printing press inks. Certain foils sold under the name Ozachrome have proved to be very helpful as a guide in such correction work. These foils are manufactured in colors which match to a rather high degree, the inks which are widely used in printing. The particular shades, lightness or strengths of the inks can be matched by uniformly reducing the density of the whole sheet or foil by pretlashing each of the several colors to a suitable level of density. This level, of course, may be different for different colors. Hence, each of the separation positives, which may be corrected by hand, frequently is printed yonto a foil of the desired color. The Ozachrome foil of the prior art may be used ,and may be overlaid in register over a white background to produce the desired proof.

The printing process just described has its limitations, but has proved useful and, in fact, is used quite widely. The colors -of the foils are determined by the manufacturer, depending upon the type of coating provided by him. Since the process inks are available in a very great variety of colors, it is `usually impossible to achieve .an exact color match between Ozachrome color, which is limited in variety .and the inks used by the manufacturer. Furthermore, the prints made on diazotype foils often show discolored backgrounds. These may be caused either by premature coupling of the dye-forming components prior to processing and/or by discoloration of yother ingredients such as the stabilizing chemicals after processing. These discolorations are very apparent in applications where two or more foils are laid over one another to produce a multicolor effect.

The present invention is designed to overcome some of these difficulties. It makes available a positive working process which is suitable Ifor use on certain carrier layers having a reasonably high degree of light sensitivity. It is usable, moreover, in ordinary room illumination.

It is a further object of this invention to make available a good method whereby the color, or colors, used in making positive prints can be matched very exactly -to a predetermined standard, both in density and in hue.

A still further object is to provide a high contrast, high resolution, and grainless copying media of very high printing speed. The image density, unlike the diazotype, is not explicitly related to the amount of light-sensitive material present in, or photodecomposed in, the light-sensitive layer. Hence, images of high visual and actinic Opacity can be produced without sacricing printing speed.

The new process of this invention is a direct copying method. It yields positive images from positive originals. Furthermore, the choice of primary and individual colors is practically unlimited.

The process of this invention, therefore, employs a layer of a compatible mixture of two major ingredients. One is a copolymer formed from about 1 mole of methylvinyl ether and 1 mole of maleic anhydride. This is referred to for brevity as PVM/MA. The other ingredientV is some other hydrophobic resin or mixture yof resins. This layer, composed of these major ingredients, may be called the carrier layer. The carrier layer may be hydrolyzed and rendered hydrophilic by any suitable process, for example, the process described in UQS. 'Patent 2,756,- 163. It may be subsequently dyed or the dyeing and hydrolyzing operations may be combined into a single operation by obtaining -a solution of a dye in the hydrolyzing material. The dyes are selected to yield the proper hue and the dye density can be readily controlled by the dyeing time or the dye concentration, or by both. Dyes which are found to be suitable for this purpose include: Color Index Basic Yellow 1, 2, 4, 10, 1l; Color Index Basic Orange 14, 22; Color Index Basic Red l, 2, 5, 9, 13; Color Index `Basic ViOle-t l, 3, 4, 5, 7, 1 0, 14; Color Index Basic Blue l, 5, 6, 9, l2 and Color Index Basic Green 1, 4.

Still another scheme by which the carrier layer may be dyed, consists lof forming an azo dye, or a plurality of azo dyes, in situ in the carrier layer. This may be accomplish'ed by impregnating the carrier layer with the dyeforming components (diazo) and coupler )and subsequently rendering the system alkaline, whereupon the dye forms. Among those diazonium compounds which have been found to be suitable for this purpose, mention may be made of the following diazotized amines; ortho-anisidine; 2,'6-dimethoxyaniline; 2,4-dimethoxyaniline; orthophenetidine; 3,3-dimethoxy-4,4-diaminobiphenyl; 2-chloro-5-trilluoromethylaniline; 2-hydroxy-4-methyl-7-aminoquinoline; 4 iaminobiphenyl; N,N diethylamine paraphenylenediamine; 4-(N,Ndiethylamino)2 ethoxy aniline; 4-(N,N-diethylamino)-Z-methylaniline; 4-ethylaminO-S-methylaniline; and the like. Among those coupling compounds which we have found to be suitable, mention may be made of: beta-naphthol-3,-disulfonic acid; 2,7- dihydroxynaphthalene; 2,S-dihydroxynaphthalene; 2,3-dihydroxynaphthalene-6-sulfonic acid; phenylmethyl pyrazolone; phloroglucinol; 5,5-dimethyl-L3-cyclo -hexanedione; m-hydroxyphenylurea, 7-hydroxy-1,2-naphthimida1 zole; resorcinol; 4,6-dichlororesorcinol, resorcinol sulfonic acid; and the like. Ammonia fumes have been found to be particularly suitable for rendering the system alkaline.

The carrier layer is then sensitized by coating it with a solvent solution containing the light-sensitive sensitizer. Sensitizers which have been found to be suitable include the water-insoluble, light-sensitive amides and esters of 2- diazo-l-naphthol-S-sulfonic acid. The adhesion of the sensitizing layer may be controlled by the addition of compatible resins, such as vinyl acetate, copolymers ofrvinyl acetate and crotonic acid, cellulose acetate, and the like, as well as by the addition of small amounts of active solvents for the dyed carrier layer, such as acetone, ethyl acetate, methyl Cellosolve acetate, and the like, to an essentially non-penetrating solvent. Y

In use, a sheet of the sensitized material is exposed beneath a positive original to a source rich in ultraviolet radiation, such as a carbon or mercury arc. The exposed sheet is then developed with a solution which removes the photoproducts and resin(s) in the irradiated areas, laying bare the dyed carrier layer. The general nature of this development process is more fully described in U.S. yPatent 2,772,972. The developed sheet is then immersed in a bleaching bath. The nature of the bleach employed, and its concentration, may v-ary somewhat according to the dye to be bleached. However, bleaches such as bromine water, hypochlorite, hydrosulfite, and the like, are usually satisfactory. A simple test may be employed -to -determine whether a particular bleaching agent is suitable. When the bleaching action is complete, the sheet is rinsed in water to remove excess reagent and wiped dry.

vThe photomechanical layer remains intact through these oper-ations, lbut may be removed at this point with a solvent which dissolves it, but does not dissolve the carrier layer or the dye. Solvents suitable for this purpose are benzene, toluene, xylene, oarbon tetrachloride, methyl-isobutyl ketone, andthe like.

The invention will be more fully understood by reference to the accompanying drawings wherein FIGS. l to 7 show diagrammatically and in exaggerated cross-sectional thickness, the sequential steps involved in preparing an intermediate yaccording to this invention.

FIG. 1 shows a base or support layer which may be film or paper of any suitable type indicated at 10. This is coated with'a carrier layer 11 which, as mentioned above, preferably consists of a mixture of a copolymer of vinylmethyl ether `and maleic anhydride combined with another compatible resin which is somewhat hydrophobic. Y FIG. '2 shows the same support 10, carrier layer 11, and a color layer of dye 12. This is applied, las previously mentioned, by first treating the carrier layer with an alkaline agent such as gaseous yammonia or aqueous sodil um hydroxide to render it somewhat hydrophilic.

FIG. 3 shows the same layers 'with ran additional layer 13 of sensitizing material which is to be exposed to actinic."

light.

FIG. 4 shows the assembly of FIG. 3 with a positive originalk14 superimposed so that light may be exposed on the sensitive layer. That part of the image which is exposed is essentially decomposed at 13e.

The actinic light showing through the clear area of theV original impinges -on the layer 13 kand this layer, where the light Vstrikes it, decomposes. Y

Now referring to FIG. 5, the decomposed area (13e of FIG. 4) has been removed from the irradiated area, leaving an opening 13j, in the top layer 13. This exposes the dye layer 12. Inother respects, the layers of FIG. are the same as in the preceding Iigures.

FIG. 6 shows the results of the bleaching operation; the photomechanical layer 13, like a stencil, permits bleaching Yonly the bared areas. The color, then, has been removed from layer 12 over area 13g and still remains in the protected areas. The 1ayer11 swells somewhat, partially lling the recess left by opening 13f, FIG. 5.

Finally, FIG. 7 shows the photomechanical layer 13 completely removed. Color has been bleached in the area 13g of layers 11, 12, as in FIG. 6; however, the bleaching was not effective on the color in the -areas of layer protected by the stencil during the bleaching. Hence, it remains in its full color. The invention will be better understood by reference to the following examples.

EXAMPLE I A preformed film of cellulose acetate manufactured by the Ansco Division of General Aniline & Film Corporation, Binghamton, New York, was coated by the reverse yroll method with the following solution:

Parts by weight of polyvinylmethyl ether maleic anhydride copolymer 4.5 Parts by weight of cellulose acetate 5.5 Parts by volume of acetone larts by volume of ethanol 40 Parts by volume of methyl Cellosolve 20 After drying, hydrolysis was effected by immersion in a dilute solution of ammonia and the iilm again dried. A lm prepared in this manner is hydrophilic and may be dyed with basic dyes.

A sheet of this film was immersed in a dye bath containing: p Water ml 800 Ethylene glycol Y ml 200 Methylene blue gm 2 Dethanolamine ml 2 sulfonamide gm 2.0 Vinylite AYAC (Bakelite) gm 0.8 Vinylite VMCH (Bakelite) gm-- 0.2 Acetone ml l5 Methyl Cellosolve acetate ml 20 Methyl-isobutyl ketone ml 65 Y rnl.

Monoethanolamine 1.5 Triethanolamine 10.0 Glycerine 25.0 Ethylene glycol V63.5

The red and blue developed foils were then immersed in a tray containing: Y

and the yellow -foil in a tray containing: 1 m Clorox (5.25% sodium hypochlorite by Weight) 50 Water 200 The dyes were bleached to substantially total absence of color in an imagewse way within 30 seconds. The foils were then thoroughly rinsed withwater and dried. The remaining portions of the upper photomechanical layer were then removed with methyl-isobutyl ketone. The unbleached portions of color were thus brought into view. When these foils were overlaid in register on one another over a white sheet of paper, a very pleasing color proof resulted.

EXAMPLE l1 A lilrn was lacquered and hydrolyzed as in Example I. The carrier layer was then dyed in a solution containing:

Water ml 900 Ethylene glycol ml 100 Genacryl Blue 6G gm 3 Diethanolamine ml 1 for about 20 seconds. It was then rinsed with Water and dried. (An equal amount of Crystal Violet AX can be substituted for the Genacryl Blue 6G.) The dyed carrier layer was then sensitized as in Example I, and the coating dried. The sensitized foil was then exposed beneath a positive original and subsequently developed by swabbing it with a solution Containing:

ml. Diethanolamine Glycerine 15 Ethylene glycol 70 This treatment removed the photoproducts and resins from the carrier layer in an imagewise way. The developed foil was next immersed in a solution containing:

Amonia water-28 B. ml 10 Water ml 90 Sodium hydrosulte gm 10 which bleached the dye in areas where. the carrier layer had been laid bare. The foil was then thoroughly rinsed with water, wiped dry, and the residual sensitizing layer was removed with toluene. After a final drying, a brilliant blue, positive copy of the original on a clear background resulted.

EXAMPLE lIII A sheet of film was lacquered as in Example I. It was then immersed in a dye bath containing:

Water ml 700 Ethylene glycol ml 300 Monoethanolamine ml 25 Methylene Blue gm 3 for about 30 seconds, The sheet was then rinsed and dried. In this manner, the intermediate hydrolyzing operation can Vbe eliminated. This dyed foil can be sensitized, processed, bleached, etc. as in Example II.

EXAMPLE IV A preformed film of polystyrene (0005") was coated with a solution comprising:

PVM/MA gm 3.0 Resin C-3, V-3O (Monsanto) gm 2.0 Ethyl acetate ml Methyl Cellosolve ml 8O and thoroughly dried. The lm Was then immersed in a dilute ammonia solution to render the carrier layer hydrophilic and the film was dried again. The carrier layer was then dyed 20 seconds in a bath containing:

Water ml 750 Ethylene glycol ml 250 Thioiiavine TCND gm 5 Monoethanolamine ml 1 rinsed with water and dried.v The dyed carrier layer was then sensitized by coating it with a solution comprising:

Vinylite AYAC (bakelite) gm 0.8 Cellulose acetate (Hercules grade LL-l) gm 0.2 Diazo compound of `the structure gm 2.0

CH2- CH2 N l l 0\ /0 CH SIOzNH Milliliters Methyl ethyl ketone 2O Methyl-isobutyl ketone 70 Methyl Cellosolve 10 and dried. The sensitized foil was then exposed beneath a positive original to the radiation of a mercury arc. The exposed foil was then developed with a solution containing:

Milllliters Monoethanolamine 5 Diethanolamine 10 Glycerine 25 Ethylene glycol 60 whereupon the photoproducts -and resins in the irradiated areas were removed imagewise. The developed sheet was next immersed in a solution containing:

Milliliters Clorox 100 Water 200 until the dye had bleached imagewise and subsequently thoroughly rinsed with water and wiped dry. A treatment with methyl-isobutyl ketone removed the residual sensitizing layer. After a nal drying, a yellow positive copy resulted, the image portions of which were suiciently opaque for making additional diazotype copies.

EXAMPLE V A sheet of the lacquered and lhydrolyzed lm employed in Example IV was immersed in `a dye bath containing:

Water ml 500 Ethylene glycol ml 200 Diethanolamine ml 1 Brilliant green crystals gm 3 for about 2O seconds. After a rinse W-ater to remove ex cessive dye solution, the ihn was dried, The dyed carrier layer was then sensitized by coating it with a solution comprising:

and dried. A sheet of this sensitized lm was then exposed, developed and processed -as was done in Example IV. A bright green positive image on a clear background resulted.

7 EXAMPLE v1 A sheet of lrn, lacquered and hydrolyzed as in Exam' ple I, was dyed in a solution containing:

Water l Y ml 750 Ethylene glycol ml Y 250 Safranine Y gm 4 Diethanolamine ml 2 for about 2O seconds, Vand then rinsed with water. After After drying, this sheet was exposed, developed and processed as in Example 4. A bright red positive copy on a clear background resulted.

EXAMPLE VII A sheet of the lacquered and hydrolyzed lm as prepared in Example I was coated with a solution containing:

Water ml t 85 Ethylene glycol ml 10 Isopropyl alcohol ml 5 Citric acid gm 3 Meta-hydroxyphenylurea gm 3 Thiourea gm 1 Diazotized para-phenetidine gm 2 Saponin gm 0.2

After drying, this sheet was subjected to moist ammonia fumes, which caused a yellow azo dye to form Within the carrier layer. The cartier layer was subsequently sensitized, exposed, developed and processed as in Example IV. A yellow positive copy on a clear backgroundvresulted. This image had suicient actinic opacity to make additional diazotype prints.

It will be obvious that variations may be made in the procedures described above Iand that substitution, which would occur -to those skilled in the art, can be made without departing from the spiritof the invention. It is intended by the claims, which follow, to cover such varia,-

tions as would occur to those skilled in the art so tarY resin compatible therewith, treating said carrier layerV with an alkaline material to render it more hydrophilic, dyeing said carrier layer with an intense color by imbibing it with the solution of a basic dye, covering said dyed carrier layer with a light-decomposable sensitized `layer by overcoating said dyed layer with a water-insoluble adhesive resin and a light-sensitive, water-insoluble diazo oxide, exposing said'sensitized layer toa colored original, removing the light-decomposed portion of said sensitized diazo oxide layer to expose a portion of the dyedgcarrierV layer, chemically bleaching the dye from said exposed portion and stripping the remainder of said sensitized ldiazo oxide layer to leave a dyed positive image of said colored original.

2. The process of forming a direct positive image by Y diazotype reproduction which comprises forming, on a suitable base, a carrier layer composed of a mixture of a copolymer of vinyl methyl ether with maleic anhydride and of another hydrophobic resin, treating said carrier layer with a moist base to render it hydrophilic, dyeing said treated hydrophilic layer with a solution of a basic dye, Vapplying a light-decomposable sensitized diazo oxide layerr over said carrier layer, exposing the sensitized layer to actinic radiation from -a colored original, removing by washing the light-decomposed portions of said sensitized diazo oxide layer to lay bare the dyed carrier layer, chemically bleaching the dye from said bare portions and causing the bleached area to swell, and stripping the undecomposed portion of said sensitized diazo oxide layer to leave a dyed positive image of said original.

3. Process according to claim 1 wherein the carrier layer comprises a mixture of vinylrnethyl ether copolymerized with maleic anhydride and a hydrophobic resin.

4. ProcessV according to claim 2 wherein the dye is closely color-matched with available printing ink, whereby the original color may be faithfully reproduced.

References Cited UNITED STATES PATENTS 2,051,603 8/1936 Hruska 96-43 2,537,097 1/1951 Slifkin 96-75 2,993,788 7/ 1961 Straw et al. 9613 3,091,528 5/1963 Buskes 96-75 3,136,637 6/1964 Larson 96-33 X 3,164,468 l/ 1965 Moskowitz et al. 96-49 3,211,553 10/1965 Ito 96-75 3,228,768 1/11966 Straw et al. 96-91 NORMAN G. TORCHIN, Primary Examiner.

J. T, BROWN, C. BOWERS, Assistant Examiners. 

1. THE PROCESS OF DIRECT POSITIVE COLOR REPORDUCTION WHICH COMPRISES FORMING ON A BASE, A CARRIER LAYER COMPRISING A HOMOGENEOUS MIXTURE OF A COPOLYMER OF A VINYL ALKYL ETHER AND MALEIC ANHYDRIDE AND A HYDROPHOBIC RESIN COMPATIBLE THEREWITH, TREATING SAID CARRIER LAYER WITH AN ALKALINE MATERIAL TO RENDER IT MORE HYD OPHILIC, DYEING SAID CARRIER LAYER WITH AN INTENSE COLOR BY IMBIBING IT WITH THE SOLUTION OF A BASIC DYE, COVERING SAID DYED CARRIER LAYER WITH A LIGHT-DECOMPOSABLE SENSITIZED LAYER BY OVERCOATING SAID DYED LAYER WITH A WATER-INSOLUBLE ADHESIVE RESIN AND A LIGHT-SENSITIVE, WATER-INSOLUBLE DIAZO OXIDE, EXPOSING SAID SENSITIZED LAYER TO A COLORED ORIGINAL, REMOVING THE LIGHT-DECOMPOSED PORTION OF SAID SENSITIZED DIAZO OXIDE LAYER TO EXPOSE A PORTION OF THE DYED CARRIER LAYER, CHEMICALLY BLEACHING THE DYE FROM SAID EXPOSED PORTION AND STRIPPING THE REMAINDER OF SAID SENSITIZED DIAZO OXIDE LAYER TO HAVE A DYED POSITIVE IMAGE OF SAID COLORED ORIGINAL. 